.\" $Id: PAPI_read.3,v 1.14 2004/10/04 03:31:01 jthomas Exp $
.TH PAPI_read 3 "September, 2004" "PAPI Programmer's Reference" "PAPI"

.SH NAME
PAPI_read \- read hardware counters from an event set
.LP
PAPI_accum \- accumulate and reset counters in an event set

.SH SYNOPSIS
.B C Interface
.nf
.B #include <papi.h>
.BI "int\ PAPI_read(int " EventSet ", long_long *" values ");"
.BI "int\ PAPI_accum(int " EventSet ", long_long *" values ");"
.fi
.B Fortran Interface
.nf
.B #include "fpapi.h"
.BI PAPIF_read(C_INT\  EventSet,\  C_LONG_LONG(*)\  values,\  C_INT\  check )
.BI PAPIF_accum(C_INT\  EventSet,\  C_LONG_LONG(*)\  values,\  C_INT\  check )
.fi

.SH DESCRIPTION

These calls assume an initialized PAPI library and a properly added
event set.

.B PAPI_read()
copies the counters of the indicated event set into 
the array
.IR values .
The counters continue counting after the read.
.LP
.B PAPI_accum()
adds the counters of the indicated event set into the array
.IR values .
The counters are zeroed and continue counting after the operation.
.LP
Note the differences between PAPI_read() and PAPI_accum(), 
specifically that PAPI_accum() resets the values array to zero.


.SH ARGUMENTS
.I EventSet
--  an integer handle for a PAPI Event Set as created by
.BR "PAPI_create_eventset" (3)
.LP
.I *values
-- an array to hold the counter values of the counting events

.SH RETURN VALUES
On success, these functions return
.B "PAPI_OK."
 On error, a non-zero error code is returned.

.SH ERRORS
.TP
.B "PAPI_EINVAL"
One or more of the arguments is invalid.
.TP
.B "PAPI_ESYS"
A system or C library call failed inside PAPI, see the 
.I "errno"
variable.
.TP
.B "PAPI_ENOEVST"
The event set specified does not exist.

.SH EXAMPLES
.nf
.if t .ft CW
  do_100events();
  if (PAPI_read(EventSet, values) != PAPI_OK)
    handle_error(1);
  /* values[0] now equals 100 */
  do_100events();
  if (PAPI_accum(EventSet, values) != PAPI_OK)
    handle_error(1);
  /* values[0] now equals 200 */
  values[0] = -100;
  do_100events();
  if (PAPI_accum(EventSet, values) != PAPI_OK)
    handle_error(1);
  /* values[0] now equals 0 */
.if t .ft P
.fi

.SH BUGS
These functions have no known bugs.

.SH SEE ALSO
.BR PAPI_set_opt "(3), " PAPI_reset "(3), " 
.BR PAPI_start "(3), " PAPI "(3), " PAPIF "(3)"
